Cystic fibrosis is a deadly hereditary disease. With one in 20 people carrying the recessive gene, conception of a child having cystic fibrosis results in approximately one in every 400 child-bearing marriages. No cure for the disease has yet been discovered. Cystic fibrosis affects the mucus secreting glands of the body, leading to an overproduction of mucus. The lungs are continuously filled with the excess mucus, which in turn must be removed daily to reduce the build-up and the risk of infection. Presently, treatment generally involves an aerosol therapy three or four times a day to obtain bronchial drainage and a daily physical pounding on the chest wall to loosen mucus for expectoration. Daily treatment can range from four to six hours plus and necessitates a respirator therapist or at least a trained individual to provide the pummeling of the chest.
The art in the area of mechanical vibrations to the body shows such things as inflatable jackets or garments to put on a person to aid in respiration, such as artificial respiration. U.S. Pat. Nos. 3,043,292, 2,354,397, 2,588,192 are representative. Additionally, a garment which provides oscillations for the purpose of massaging the body is shown in U.S. Pat. No. 3,310,050.
In more recent years, a variety of high frequency chest compression (“HFCC”) systems have been developed to aid in the clearance of mucus from the lung. Such systems typically involve the use of an air delivery device, in combination with a vest to be worn by a patient, with the two being connected by a valve or other device that permits the pulsed flow of air to the vest. Such vests were developed for patients with cystic fibrosis, and are designed to provide airway clearance therapy. The patient wears an inflatable vest that is linked to an air pulse generator that rapidly inflates and deflates the vest during inspiration and/or expiration. The compression pulses produce transient cephalad air flow bias spikes in the airways, which moves mucous toward the larger airways where it can be cleared by coughing. The prior vest systems differ from each other, in at least one respect, by the valves they employ (if any), and in turn, by such features as their overall weight and the wave form of the air produced.
Related patents describe systems having a variety of attributes, e.g., those in which an air stream is interrupted, as by the use of a regenerative blower with a rotary interrupt valve. Such systems are typified by a “quick dump”, high volume rotary valve (also known as a “tube valve” or “chopper valve”). These types of valves typically produced a pulse form that most closely approximated near square wave pulses at about 10 to 20 Hz (i.e., not true sine waves), but which are said to become more sinusoidal as the frequency is decreased to 5 Hz.
U.S. Pat. No. 4,838,263 (Warwick et al.) describes an apparatus in which the application of pressurized pulses and the pulse rate are each controllable by the patient. The device addresses the desire of some patients to have the device provide less of a “thump” during inhalation. The device, in turn, permits the user to controllably cut the thumping pressure. In operation, the tank delivers air into the bladder, and the patient uses either a pedal to deliver more air and/or a thumb positioned over a tube, in order to release pressure.
U.S. Pat. No. 5,056,505 for a “Chest compression apparatus”, invented by Warwick and Hansen relates to an oscillatory chest compression apparatus to aid in loosening and eliminating mucus from the lungs of a cystic fibrosis patient. The '505 patent describes an apparatus, including a valve that can be used to deliver a sharply spiked air pulse, such that the slope (rise time) of the pulse is defined as being at least twice as fast as that of a sinusoidal wave of the same frequency and amplitude. The valve itself involves the use of leading and following edges that serve to abruptly start and stop the flow of air. During inspiration, the atmospheric phase, the positive pressure side of the system can be blocked. The pressure pulse wave form is a function of the shape and size of the rotary valve ports and the pressure applied to the valve. The quick dump design of the valve ports allows for maximum opening in a short time. A constant pressure air stream is chopped into pulses and directed to the inflated vest.
Hansen U.S. Pat. No. 5,569,170 (assigned to Electromed, Inc. Minnetonka, Minn.) is directed to yet another alternative in which a speaker-like diaphragm is employed to deliver the pulses in the form of repetitive pressure pulses, much along the lines of a pulsating speaker.
U.S. Pat. No. 4,977,889 (Budd), in turn, describes an algorithm for use in tuning such an apparatus to a particular patient. The algorithm can be used to improve the effectiveness (mucous generation and air flow spikes) of any chest compression apparatus. Presently, doctors having such software can use the algorithm to set any particular device for a particular patient.
Finally, Van Brunt et al. (U.S. Pat. No. 5,769,797, “Oscillatory chest compression device”) describes a compression device that includes an oscillatory air flow generator and a positive air flow generator. A first feedback system controls the oscillation rate of the oscillatory air flow generator, and a second feedback system controls the peak pressure created by the positive air flow generator.
Certain of the approaches described above have been embodied in various prototypes and/or commercial devices that have been previously developed. Applicant's own initial “Model 101”, and later “Model 102” were developed and used previously, both employing a rotary (“chopper”) valve, of the type described in the above-captioned '505 patent. These devices provided wave forms having a near square wave pulse form.
Currently, American Biosystems, Inc. markets a device (“Model 103”) under the tradename “ThAIRapy Vest”, as a device designed for self-administration of chest physical therapy for patients with cystic fibrosis and other chronic lung disorders. The vest is said to be a portable device that uses a technology called high frequency chest wall oscillation to provide airway clearance therapy. The vest includes an inflatable vest linked to an air pulse generator that inflates and deflates the vest from 5 to 25 times per second. This creates a high expiratory flow within the lungs which moves mucous toward the larger airways where it can be cleared by coughing. The device appears to include the use of a diaphragm driven by an electromagnet, which appears to provide a sine wave pulse form.
The units presently in commercial use, however, continue to be quite expensive, as well as large and heavy, and hence are not considered particularly portable. The community of patients suffering from these disease therefore continues to seek affordable devices that can provide comparable or improved features and performance, in a manner that provides improved portability.